1. Field of the Invention
The present invention relates to a measuring apparatus' a measuring method, and a test apparatus for measuring a waveform of an output signal output from an electronic device such as a semiconductor device.
2. Related Art
There has been conventionally used a measuring apparatus for measuring a waveform of an output signal from an electronic device such as a semiconductor device in order to decide the good or bad of the electronic device. The measurement of a waveform of an output signal includes, for example, measurement of jitter of the output signal and measurement of a variation point of the waveform of the output signal.
A conventional measuring apparatus' for example when measuring jitter, continuously outputs an output signal to an electronic device multiple times detects a signal level of each output signal at a predetermined phase, and compares the detected signal level and a predetermined signal level. Then, the measuring apparatus sequentially changes a phase detecting a signal level and obtain the number of times by which a comparison result is a pass (or a fail) for each phase, in order to measure jitter of the output signal. In this case, the measuring apparatus generates a strobe signal to determine a phase detecting a signal level of an output signal and sequentially changes a phase of this strobe signal, in order to perform measurement.
Moreover, when measuring a variation point of a waveform of an output signal, a conventional measuring apparatus continuously outputs an output signal to an electronic device multiple times changes a phase of a strobe signal for each output signal, and detects a phase, at which a comparison result varies from a pass to a fail (or from a fail to a pass), as a variation point of a waveform.
Moreover, as a measuring apparatus for measuring jitter, a measuring apparatus using two strobe signals of which a phase interval is determined is known as disclosed, for example, in Patent Document 1. This measuring apparatus measures jitter distribution of an output signal by scanning the output signal with two strobe signals having a constant phase interval.
Patent Document 1 WO02-50557
However, since a conventional measuring apparatus must separately measure a jitter amount of an output signal and a variation point of a waveform of the output signal, measurement was inefficient. Moreover, a measuring apparatus using two strobe signals measures only distribution of jitter, and thus cannot measure a variation point of a waveform of an output signal and sharpness of an edge of the output signal. Moreover, it is necessary to determine a phase interval of two strobe signals to an appropriate value. For this reason, it is necessary to repeatedly perform measurement in order to determine this phase interval, and thus measurement efficiency deteriorates.